I'm wanting to build a really lightweight AR for my wife.

I was looking at buying a Cav Arms lower and building an upper with a 16" lightweight barrel and an old M16 upper with no ejection block or forward assist. Is it possible to get it under 5lbs? I don't want a carbon fiber reciever, but I would do a Cavalry Arms lower.

Your "lightweight" thoughts are requested.

14.5" M4 style carbine is pretty light compared to my HBAR.

From reading lightweight threads in the past I've gathered ~5 pounds is the wall without sacrificing reliability.

This one's 5.0 pounds:


Weight saving particulars include:
• Cav Arms polymer lower
• 14.5" pencil barrel w/a permanent Phantom FH and a micro gas block
• Young skeletonized N/M bolt carrier
• 9mm flattop upper (no forward assist or brass deflector) with a gas tube hole drilled by ADCO
• PRI carbon fiber free float tube
• Magpul polymer MBUS front and rear

It has never had any sort of malfunction with its single stage nonadjustable Jard trigger, but be aware that a couple of two stage triggers had reset difficulties in that lower.

I found the Les Baer flattop with no forward assist, but was thinking old slickside upper with A1 sights. I hadn't thought of using a 9mm upper. Are there any other mods besides the gas tube hole that has to be done. Seems like I could drill a hole with a center cutting endmill on my mini-mill.

So, the Young BC is lighter than a regular AR15 BC? If so, did you have to use a different buffer/spring?

I will be using iron sights. What do you think of the Magpuls?

Thanks for sharing.

If I did go with a dot I would use the Aimpoint T1 Microdot, too.

I am leaning towards using the regular FSB on my build so I would only need the rear.

All other items the same, which would you say is lighter: the 9mm Model1sales upper with a rear magpul, or a slickside with the A1 sight/carry handle?

Thanks for the help my friend.
God bless Texas!

The slickside 9mm flattop with ejection port door and the Magpul MBUS weighs 8.0 ounces. Perhaps someone in the Retro Forum can tell you how much a slickside A1 (604) upper receiver weighs with port door and sight installed.


6 5/8 oz. + 1 3/8 oz. for the MBUS

They are pretty close, but the 9mm gives you more options.

I had a 604 upper (slick side A1) with rear sight assembly and port door on my bench.  It weighs about 8.25 ounces.  (The port door isn't attached, just placed there for the weight)